Contact-free potentiometer

ABSTRACT

A stationary elongated armature body and a permanent magnet are connected in a magnetic circuit. A guide plate of non-magnetic material is interposed between the armature body and the magnet. The guide plate is adjacent the armature body and has a recess formed therethrough and a galvanomagnetic resistor is embedded in the recess. The guide plate guides the magnet in gliding relation.

United States Patent Keller 51 July 11,1972

[54] CONTACT-FREE POTENTIOMETER 72] Inventor: Werner Keller, Olching,Germany [73] Assignee: Siemens Aktiengesellschalt, Berlin and Munich,Germany [22] Filed: Dec. 11, 1969 [21] Appl. No.: 884,167

[30] Foreign Application Priority Data Dec. 17, 1968 Germany ..P l8 15160.5

[5 2] US. Cl. ..338/32 R, 323/94 H [51] Int. Cl. ..H0lc 7/16 [58] FieldofSearch ..338/32, 32 H; 323/941-1 [56] References Cited UNITED STATESPATENTS 3,571,774 3/1971 l-luhvich ..338/32 R 2,752,434 6/1956 Dunlap,Jr.

3,359,522 11/1967 Albrecht et al. ..323/94 H 3,366,908 l/l968 Weiss etal ..323/94 11 FOREIGN PATENTS OR APPLICATIONS 1,185,557 3/1970 GreatBritain ..338/22 Primary Examiner-Benjamin A. Borchelt AssistantExaminer-41. Kinberg Attorney-Curt M. Avery, Arthur E. Wilfond, HerbertL. Lerner and Daniel J. Tick [57] ABSTRACT A stationary elongatedarmature body and a permanent magnet are connected in a magneticcircuit. A guide plate of nonmagnetic material is interposed between thearmature body and the magnet. The guide plate is adjacent the armaturebody and has a recess formed therethrough and a galvanomagnetic resistoris embedded in the recess. The guide plate guides the magnet in glidingrelation.

13 Claims, 7 Drawing Figures Patented July 11, 1972 CONTACT-FREEPOTEN'IIOMEI'ER DESCRIPTION OF THE INVENTION The invention relates to apotentiometer. More particularly, the invention relates to acontact-free potentiometer.

The contact-free potentiometer of the invention comprises a permanentmagnet which may be removed across a stationary armature body, and agalvanomagnetic resistor or field plate. Field plates are bodies havingelectrical resistance which may be magnetically controlled.

The principal object of the invention is to provide a new and improvedcontact-free potentiometer.

An object of the invention is to provide a contact-free potentiometerwhich includes a field plate adjustable to provide a desired resistancemagnitude which may be reproduced at any time.

An object of the invention is to provide a contactfree potentiometerhaving a resistance magnitude which, once adjusted, may be maintainedwithout variation for a long period of time.

An object of the invention is to provide a contact-free potentiometerhaving a resistance magnitude which, once adjusted, may be maintainedwithout variation for more than fifteen years.

An object of the invention is to provide a contact-free potentiometerwhich is sealed dust tight and is shielded against outside magneticfields.

An object of the invention is to provide a contact-free potentiometerwhich is almost completely insensitive to production tolerances.

An object of the invention is to provide a contact-free potentiometer inwhich a layer of non-magnetic material interposed between the armaturebody and the magnet creates a space between said armature body and saidmagnet, which remains constant in each position of the magnet, therebypreventing the accumulation of foreign bodies between said armature bodyand said magnet, so that the potentiometer remains almost completelyinsensitive to production tolerances.

An object of the invention is to provide a contact-free potentiometerwhich functions with efficiency, effectiveness and reliability.

In accordance with the invention, a contact-free adjustablesemiconductor potentiometer has a plate-shaped galvanomagneticsemiconductor resistor whose resistance may be determined by shifting amagnetic field in operative proximity therewith. The magnetic field isproduced by a magnetic circuit having a permanent magnet and astationary elongated armature. The potentiometer comprises a guide plateof nonmagnetic material interposed between the magnet and the armaturebody. The guide plate has a recess formed therein and thegalvanomagnetic resistor is embedded in the recess. The guide plateguides the magnet in gliding relation.

The guide plate comprises a U-shaped frame aflixed to the armature bodyand forming a tunnel-like housing therewith enclosing the area of themagnet.

The guide plate comprises a brass sheet and is cemented to the armaturebody. The magnet comprises a permanently magnetic cylindrical rod havinga pair of wafer-like poleshoes.

The guide plate further comprises a spring bolt mounted between themagnet and abutting against the frame. The guide plate further comprisesa spiral spring in the area enclosed by the frame and abutting an axialend of the magnet whereby the magnet is movable relative to the spiralspring.

A container of substantially hollow cylindrical configuration has aclosed bottom base and an open top base and encloses the potentiometerwith the spiral spring adjacent the bottom. A cover of substantiallyhollow cylindrical configuration has an open bottom base and a closedtop base and is adapted to engage the container in a threadlike manneras a micrometer screw.

The guide plate further comprises a spherical member mounted on theopposite axial end of the magnet between the magnet and the cover andabutting the magnet and the cover. The container has a groove formedtherein and the cover has at least one bolt engaging the groove.

The cover has a border area on its cylindrical surface. The cover has arecess formed in its top surface adapted to receive an adjusting tool.The cover has a ring shiftably mounted on its cylindrical surface andhaving a scale division thereon.

In order that the invention may be readily carried into effect, it willnow be described with reference to the accompanying drawing wherein:

FIG. 1 is a view, partly in section, of an embodiment of thecontact-free potentiometer of the invention;

FIG. 2 is a side view of the enclosed contact-free potentiometer of theinvention;

FIG. 3 is a top view of the embodiment of FIGS. 1 and 2, with the coverremoved;

FIGS. 4 and 4a illustrate the two extreme positions of the magnet andarmature body relative to each other; and

FIGS. 5 and 5a are two views of the layer of non-magnetic materialillustrating the position of the galvanomagnetic resistor.

In the FIGS, the same components are identified by the same referencenumerals.

As shown in FIGS. 1, 2 and 3, an armature body 4 is formed of anon-ferrous, substantially planar, iron rod. The armature body 4 isaflixed to a U-shaped metal frame 8 and defines with said frame ahousing which encloses the area of a magnet l, 2, 3.

The magnet l, 2, 3 is a permanent magnet mounted for movement in axialdirections alongside the armature body 4 within the housing formed bysaid armature body and the U- shaped frame 8. The magnet comprises apermanently mag netic cylindrical rod 1 having a first wafer-likepoleshoe 2 at the upper end thereof and a second wafer-like poleshoe 3at the lower end thereof.

A spring bolt or buckle 9 is affixed to the poleshoes 2 and 3 of themagnet 1, 2, 3 and abuts the inside surface of the U- shaped frame 8.The spring bolt 9 thereby urges the magnet 1, 2, 3, in addition to themagnetic force at the areas of the poleshoes 2 and 3 of said magnet,against a layer of non-magnetic material 5. The layer of non-magneticmaterial 5 is interposed between the annature body 4 and the magnet l,2, 3 and comprises a thin brass sheet cemented to said armature body.

A recess 6 (FIGS. 5 and 5a) is formed through the layer 5 ofnon-magnetic material. A galvanomagnetic resistor or field plate 7(FIGS. 4 and 4a and 5 and 5a) is embedded in the recess 6 formed in thelayer 5 of non-magnetic material.

The magnet l, 2, 3 and the metal frame 8 are housed in a steel container13 of substantially hollow cylindrical configuration having a closedbottom base and an open top base. The magnet l, 2, 3 is movable in thecontainer 13 in axial directions thereof and in gliding relation on thenon-magnetic layer 5. The magnet l, 2, 3 is thus movable between aposition in which it is at a minimum or maximum distance from thegalvanomagnetic resistor 7 positioned in the recess 6 of the nonmagneticlayer 5 and the maximum or minimum distance from said galvanomagneticresistor.

A spiral spring 14 is positioned around the lower end of the magnet l,2, 3 between the second poleshoe 3 of said magnet and the inside surfaceof the container 13 and abuts said poleshoe and said container. A steelcover 10 covers and seals the container 13. The cover 10 is ofsubstantially hollow cylindrical configuration having an open bottombase and a closed top base and adapted to engage the container 13 in athreadlike manner as a micrometer screw.

The edge of the cover 10 which partly surrounds the container 13 isjoined by bolts with said container. The housing provided by thecontainer 13 and the cover 10 provides, without additional measures, andin an advantageous manner, a dusttight sealing of the potentiometer andcomplete protection against interfering magnetic fields.

manually rotated, with the assistance of a milled or border area 31(FIG. 2) on its cylindrical surface, or with the assitance of ascrewdriver or other suitable tool. The screwdriver is accommodated by arecess 30 formed in the outer top surface of the cover 10.

The rotating movement of the cover is translated into an axial movementof the magnet 1, 2, 3 via the spherical member 1 1. A specific threadingpitch between the container 13 and the cover 10 is selected to enablethe adjustment and setting of the potentiometer at a desired precision,without the requirement for additional measures such as, for example,gears. The rotation of the cover 10 is limited by bolts 12 provided inthe engaging edge of the cover 10 and functioning as stops for engaginga groove 25 formed in the container 13. The bolts 12 also prevent thehousing from being unintentionally disturbed by preventing the cover 10from being unintentionally removed from the container 13. The tighteningof at least one bolt at the surface of the container may prevent anadjusted resistance value from undesired variation.

In the final positions of movement determined in this manner, the magnet1, 2, 3 is positioned at a maximum and a minimum distance from thegalvanomagnetic resistor 7 positioned in the recess 6 of thenon-magnetic layer 5. The maximum position of the cover 10 isillustrated by broken lines in FIG. 2.

The left-hand view of FIGS. and 4a illustrates the minimum position inwhich the magnet 1, 2, 3 is a minimum distance from the galvanomagneticresistor 7. In the minimum position, the second poleshoe 3 of the magnetl, 2, 3 covers the field plate 7 completely, so that said field plate issubjected to a maximum flux. The right-hand view of FIGS. 4 and 4aillustrates the maximum position in which the magnet l, 2, 3 is amaximum distance from the galvanomagnetic resistor 7 positioned in therecess 6 of the non-magnetic layer 5. In the maximum position, thesecond poleshoe 3 is a maximum distance from the field plate 7, so thatthe magnetic flux to which said field plate is subjected is almost zero.

The play or clearance in the threading between the container l3 and thecover 10 of the housing of the potentiometer of the invention iscanceled out or compensated for in a preferred manner by the spiralspring 14. The setting or reading of a specific resistance value isprovided with the assistance of two scale marks and 16 provided on theoutside of the potentiometer housing in the same manner as for amicrometer screw. One scale mark 15 is positioned on a ring 17 aroundthe cylindrical surface of the cover 10 and may be shifted thereon. Thedistance between the scale marks may be selected in a manner whereby anydesired exact adjustment may be effected for desired resistance values.After adjustment, the ring 17 may be cemented to the cover 10.

Electrically conductive leads 18 extend from the potentiometer housing,through the bottom of the container 13 thereof, to the outside. Awinding 19 is positioned around the permanent magnet rod 1 in order toadjust the magnetic field. The two ends of the winding 19 are connectedto electrically conductive leads which extend from the potentiometerhousing through the bottom of the container 13 thereof via electricalcontacts 21. One of the leads 20 from one of the ends of the winding 19is shown in FIG. 3. The bottom of the container 13, as shown in FIG. 3,is provided with bolts or screws 22, 23 and 24 for fixing the variouscomponents of the potentiometer of the invention in position in thepotentiometer housing.

While the invention has been described by means of a specific exampleand in a specific embodiment, I do not wish to be limited thereto, forobvious modifications will occur to those skilled in the art withoutdeparting from the spirit and scope of the invention.

I claim: 1. A contact-free, adjustable semiconductor potentiometerhaving a plate-shaped, galvanomagnetic semiconductor resistor whoseresistance may be determined by shifting a magnetic field in operativeproximity therewith, the magnetic field being produced by a magneticcircuit having a permanent magnet and a stationary elongated armaturebody, said potentiometer comprising a guide plate of non-magneticmaterial interposed between the magnet and the armature body of themagnetic circuit, said guide plate being adjacent to the armature bodyand having a recess formed therein and said galvanomagnetic resistorbeing embedded in said recess, said guide plate guiding the magnet ingliding relation.

2. A contact-free potentiometer as claimed in claim 1, wherein saidguide plate comprises a U-shaped frame affixed to said armature body andforming a tunnel-like housing therewith enclosing the area of saidmagnet.

3. A contact-free potentiometer as claimed in claim 1, wherein saidguide plate comprises a brass sheet and is cemented to said armaturebody.

4. A contact-free potentiometer as claimed in claim 1, wherein saidmagnet comprises a permanently magnetic cylindrical rod having a pair ofwafer-like poleshoes.

5. A contact-free potentiometer as claimed in claim 2, wherein saidguide plate further comprises a spring bolt mounted between said magnetand abutting against said frame.

6. A contact-free potentiometer as claimed in claim 2, furthercomprising a spiral spring in the area enclosed by said frame andabutting an axial end of said magnet whereby the magnet is movablerelative to the spiral spring.

7. A contact-free potentiometer as claimed in claim 6, furthercomprising a container of substantially hollow cylindrical configurationhaving a closed bottom base and an open top base and enclosing saidpotentiometer with said spiral spring adjacent said bottom.

8. A contact-free potentiometer as claimed in claim 7, furthercomprising a cover of substantially hollow cylindrical configurationhaving an open bottom base and a closed top base and adapted to engagesaid container in a threadlike manner as a micrometer screw.

9. A contact-free potentiometer as claimed in claim 8, wherein saidguide means further comprises a spherical member mounted on the oppositeaxial end of said magnet between said magnet and said cover and abuttingsaid magnet and said cover.

10. A contact-free potentiometer as claimed in claim 8, wherein saidcontainer has a groove formed therein and said cover has at least onebolt engaging said groove.

11. A contact-free potentiometer as claimed in claim 8, wherein saidcover has a border area on its cylindrical surface.

12. A contact-free potentiometer as claimed in claim 8, wherein saidcover has a recess formed in its top surface adapted to receive anadjusting tool.

13. A contact-free potentiometer as claimed in claim 8, wherein saidcover has a ring shiftably mounted on its cylindrical surface and havinga scale division thereon.

1. A contact-free, adjustable semiconductor potentiometer having aplate-shaped, galvanomagnetic semiconductor resistor whose resistancemay be determined by shifting a magnetic field in operative proximitytherewith, the magnetic field being produced by a magnetic circuithaving a permanent magnet and a stationary elongated armature body, saidpotentiometer comprising a guide plate of non-magnetic materialinterposed between the magnet and the armature body of the magneticcircuit, said guide plate being adjacent to the armature body and havinga recess formed therein and said galvanomagnetic resistor being embeddedin said recess, said guide plate guiding the magnet in gliding relation.2. A contact-free potentiometer as claimed in claim 1, wherein saidguide plate comprises a U-shaped frame affixed to said armature body andforming a tunnel-like housing therewith enclosing the area of saidmagnet.
 3. A contact-free potentiometer as claimed in claim 1, whereinsaid guide plate comprises a brass sheet and is cemented to saidarmature body.
 4. A contact-free potentiometer as claimed in claim 1,wherein said magnet comprises a permanently magnetic cylindrical rodhaving a pair of wafer-like poleshoes.
 5. A contact-free potentiometeras claimed in claim 2, wherein said guide plate further comprises aspring bolt mounted between said magnet and abutting against said frame.6. A contact-free potentiometer as claimed in claim 2, furthercomprising a spiral spring in the area enclosed by said frame andabutting an axial end of said magnet whereby the magnet is movablerelative to the spiral spring.
 7. A contact-free potentiometer asclaimed in claim 6, further comprising a container of substantiallyhollow cylindrical configuration having a closed bottom base and an opentop base and enclosing said potentiometer with said spiral springadjacent said bottom.
 8. A contact-free potentiometer as claimed inclaim 7, further comprising a cover of substantially hollow cylindricalconfiguration having an open bottom base and a closed top base andadapted to engage said container in a threadlike manner as a micrometerscrew.
 9. A contact-free potentiometer as claimed in claim 8, whereinsaid guide means further comprises a spherical member mounted on theopposite axial end of said magnet between said magnet and said cover andabutting said magnet and said cover.
 10. A contact-free potentiometer asclaimed in claim 8, wherein said container has a groove formed thereinand said cover has at least one bolt engaging said groove.
 11. Acontact-free potentiometer as claimed in claim 8, wherein said cover hasa border area on its cylindrical surface.
 12. A contact-freepotentiometer as claimed in claim 8, wherein said cover has a recessformed in its top surface adapted to receive an adjusting tool.
 13. Acontact-free potentiometer as claimed in claim 8, wherein said cover hasa ring shiftably mounted on its cylindrical surface and having a scaledivision thereon.